I propose to employ one well studied system--the escape system of the cockroach--to investigate several current problems in neuronal plasticity and integration. We will seek to determine the role of neuronal activity in controlling the variation in the functional strength of a specific sensory pathway. We will also seek to determine the mechanisms by which ablation of one sensory organ (the left cercus) leads to the takeover of function by another sensory organ (the right cercus). We will use physiological methods to test such parameters as threshold voltage, input resistance, and passage of dendritic impulses to axons. We will also use anatomical means to determine any changes in the number and distribution of synaptic contacts at the sensory-to-giant-interneuron junctions. In addition, experiments are planned to test the idea that the two groups of giant interneurons--the dorsals and the ventrals--are used separately in the escape sequence; that is, that the principle of sequential parallel processing applies. These studies will employ killing of individual giant interneurons by intracellular pronase injection, and high speed cine analysis of subsequent escape behaviors. It is suggested that these studies on plasticity at the level of single, identified neurons can help lead the way toward a general cellular understanding of recovery of neuronal function. This work can thus contribute to understanding recovery of human neural function from lesions and sensory deprivation.